When a sealed alkaline battery is accidentally charged or overdischarged, gas may be generated in the battery, and the internal pressure of the battery may increase, resulting in a rupture of the battery. To address this problem, alkaline batteries generally include an explosion-proof valve configured to release gas generated in each of the batteries to outside the battery with an increase in the internal pressure of the battery.
A structure in which a gasket used to seal an opening of a battery case includes a thin portion, and the thin portion of the gasket is ruptured with an increase in the internal pressure of the battery to release gas generated in the battery to outside the battery has been known as the structure of the explosion-proof valve.
Incidentally, actuation of an explosion-proof valve does not only allow the release of gas generated in a battery to outside the battery, but also may simultaneously cause an electrolyte to leak or be scattered to outside the battery. An electrolyte of an alkaline battery is strongly alkaline, and thus, electrolyte leakage may cause problems, such as corrosion of a used device.
To address such problems, PATENT DOCUMENT 1 describes a technique in which in a sealed alkaline battery, a gas-permeable shielding filter is disposed inside a sealing plate to reduce the scattering of an electrolyte.
PATENT DOCUMENT 2 describes a technique in which an air-permeable and liquid impervious porous member is disposed in a space defined by a gasket and a sealing plate to prevent electrolyte leakage.